As John Coker explained elsewhere, locomotive tenders are one of the greatest marketing devices available to a steam railroad ... lots and lots of riders photograph the locomotive and then show these photographs to their friends. They may not remember what town (or even what state) they were in each day, but their pictures tell a story. As I have already commented, Union Pacific owns the name "Rio Grande", and various places share the heritage ... so it is very hard for CATS or DSNG to build a brand on anything other than who they are, and that name is what they want people to carry home with them. And the name on the tender is what people will have available when they go to Google (the last time I did a search on "Rio Grande", various sites of interest to a tourist/traveler came up before CATS did)
Cost to railroad of pictures taken by visitors $0.00
Cost to railroad of effort to distribute those pictures $0.00
Cost to railroad of excited commentary accompanying those pictures $0.00
Value of advertising all over the country = PRICELESS!!!